1. Field of the Invention
This invention relates to an image processing system and image forming apparatus for forming a color image by the image forming apparatus on the basis of data transferred from an image processing apparatus, an image processing method, and a recording medium.
2. Description of the Related Art
A conventionally known image forming apparatus for forming a color image by an electrophotographic printing method forms a color image by repeating image formation operation four times for yellow, magenta, cyan, and black planes using one photosensitive drum and one transfer drum.
In an image processing system for transferring image data from a computer and forming an image on a print sheet using this 1-drum type color image forming apparatus, the print sheet is taken up to the transfer drum, and image data for forming a yellow image is transferred to form an image. Then, image data for forming a magenta image is transferred to form an image, image data for forming a cyan image is transferred to form an image, and image data for forming a black image is transferred to form an image. The print sheet is removed from the transfer drum to fix the images, thereby printing a color image.
The image processing system using the 1-drum type color image forming apparatus requires only one pair of mechanisms necessary for forming an image, such as a photosensitive drum, and can transfer image data of the respective colors four times. Therefore, this system can form a color print with a relatively inexpensive construction without requiring any large-capacity image memory necessary for temporarily storing image data of the respective colors.
Another conventionally known color image forming apparatus for forming a color image by an electrophotographic printing method forms a color image by using four, yellow, magenta, cyan, and black photosensitive drums and performing one image formation operation for each drum.
In an image processing system for transferring image data from a computer and forming an image on a print sheet using this 4-drum type color image forming apparatus, image data of yellow, magenta, cyan, and black colors transferred from the computer are temporarily stored in image memories for the respective colors. Images are formed by sequentially reading out the image data of the respective colors from the image memories in units of colors in synchronism with convey timings of a print sheet to the respective photosensitive drums. The images are fixed to print a color image.
The image processing system using the 4-drum type color image forming apparatus can form a color image by one print sheet convey operation, thus realizing relatively high-speed printing.
However, the conventional image processing system, e.g., the construction using the 1-drum type color image forming apparatus is difficult to perform high-speed printing because image formation is repeated four times for the respective colors.
The system construction using the conventional 4-drum type color image forming apparatus can perform higher-speed printing than the 1-drum type system. However, the respective photosensitive drums are arranged apart from each other by a predetermined distance owing to the mechanism layout, and the print sheet is sequentially conveyed to the plurality of photosensitive drums. For this reason, the system must supply image data of the respective colors after correcting the time difference required for the print sheet to reach each photosensitive drum. This system must comprise a large-capacity image memory necessary for temporarily storing image data of the respective colors, resulting in high cost.